1. Field of the Invention
The present invention relates to a scanning exposure apparatus and a method of manufacturing a device using the scanning exposure apparatus.
2. Description of the Related Art
A scanning exposure apparatus generally scans at a constant speed during the exposure period for the following two reasons. First, the exposure dose on a substrate (e.g., a wafer or a glass plate) is maintained constant when the exposure rate on the substrate is constant. Second, the scanning exposure apparatus is less prone to vibrate upon stage driving as long as it has a constant speed (i.e., zero acceleration).
In recent years, an exposure apparatus is expected to achieve both a high resolution and a high productivity. As one solution to meet this demand, Japanese Patent Laid-Open No. 7-135158 discloses a scheme of exposing a substrate not only during the period in which the scanning speed stays constant but also during the acceleration and deceleration periods. This scheme adjusts the exposure rate in accordance with the scanning speed during exposure, thereby allowing exposure during acceleration/deceleration free from any exposure variation, i.e., allowing an improvement in throughput.
Japanese Patent Laid-Open No. 9-199386 discloses a technique of correcting, an image shift attributed to an orientation error, decentering, or vibration of a projection optical system, or pitching of a mask stage each upon driving the mask stage, in accordance with the scanning position and acceleration of the mask stage during exposure.
To improve the throughput, one scheme is to scan and expose a substrate not only during the period in which the speeds of an original stage and a substrate stage are controlled constant but also during the period in which the speeds of the original stage and the substrate stage change.
However, the deformations of the original stage and substrate stage attributed to changes in speed of the original stage and substrate stage are non-negligible. As the original stage and the substrate stage deform, the original and the substrate on them, in turn, deform. This results in a distortion of an image transferred onto the substrate on the substrate stage.
Japanese Patent Laid-Open No. 9-199386 neither discloses nor suggests a technique of correcting a distortion generated in an image transferred onto the substrate due to the deformations of the original stage and substrate stage.